Question 694592
You start with 3.8 liters and end with 3.8 liters
This is one of the keys.
{{{ .45*3.8 = 1.71 }}} liters of pure antifreeze to start with
Let {{{ x }}} = liters to be drained off and replaced
with pure antifreeze
{{{ .45x }}} = liters of pure antifreeze drained off.
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{{{ ( 1.71 - .45x + x ) / 3.8 = .6 }}}
{{{ 1.71 + .55x = .6*3.8 }}}
{{{ 1.71 + .55x = 2.28 }}}
{{{ .55x = 2.28 - 1.71 }}}
{{{ .55x = .57 }}}
{{{ x = 1.0364 }}}
1.036 liters of the solution should be drained and 
replaced with pure antifreeze
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check:
{{{ ( 1.71 - .45x + x ) / 3.8 = .6 }}}
{{{ ( 1.71 - .45*1.0364 + 1.0364 ) / 3.8 = .6 }}}
{{{ 1.71 - .4662 + 1.036 = .6*3.8 }}}
{{{ 1.71 + .5700 = 2.28 }}}
{{{ 2.28 = 2.28 }}}
Did I get it right?